Abstract
Opsin genes encode for opsin proteins, which are responsible for light reception in the rod and cone cells in the retina. Fishes in general show numerous visual adaptations.
Most of the fish lineages have also experienced additional whole genome duplications (WGDs) on top of the two vertebrate rounds. WGDs represent substantial evolutionary force, since they provide "genetic raw" material and in general increase genes number.
There were at least three WGD events during sturgeon evolutionary history independent of the teleost-specific genome duplications. In this study we identified opsin genes of several sturgeon species and investigated their expression level in sturgeon subclades with different WGD history and living in different habitats.
We found an exceptionally modified species, the Starry sturgeon (Acipenser stellatus), which does not express any rod opsins, and hence seems to lack rods in the retina. To visualize cone cells and their putative mosaic pattern, we applied FISH (fluorescence in situ hybridization) on the A. stellatus retina.
Further, in Sterlet (A. ruthenus; evolutionary diploid) and the Siberian sturgeon (A. baerii; evolutionary tetraploid), we had the opportunity to compare opsin gene repertoire and their expression level between pure species and their hybrids, normoploids and specimens with manipulated ploidy level, and, lastly, between pigmented and albino specimens.